In the prior art, a structure that increases convenience when entering and exiting a transit bus by eliminating steps from the entrance or exit has been proposed for a transit bus vehicle body frame. For example, patent document 1 describes a vehicle body frame including a side frame divided into a rear frame, which is located above the rear wheels, and a front frame, which is located in front of the rear wheels. The front frame is placed at a lower position than the rear frame. Then, a connection member connects the frames to each other. This eliminates the need for steps at the entrance or exit.
Recent trucks on which cargo beds are mounted also have lowered cargo beds so that more cargo can be carried within the specified size. A known side frame of a vehicle body frame for such a truck is an integrally casted frame curved near the axle to avoid the movable range of the axle.